I'd appreciate a bit of help in interpreting some server variables for
a performance comparison chapter.
With the following pdns.conf
default-ttl=3600
distributor-threads=3
launch=gmysql
log-dns-details=no
cache-ttl=3600
negquery-cache-ttl=3600
query-cache-ttl=3600
I'm getting these values:
corrupt-packets 0 Number of corrupt packets received
deferred-cache-inserts 62746 Amount of cache inserts that were
deferred because of maintenance
deferred-cache-lookup 6350 Amount of cache lookups that were
deferred because of maintenance
latency 2 Average number of microseconds needed to
answer a question
packetcache-hit 2036029
packetcache-miss 410882
packetcache-size 501350
qsize-q 0 Number of questions waiting for database
attention
query-cache-hit 158314 Number of hits on the query cache
query-cache-miss 690664 Number of misses on the query cache
servfail-packets 0 Number of times a server-failed packet
was sent out
timedout-packets 0 Number of packets which weren't answered
within timeout set
udp-answers 2450270 Number of answers sent out over UDP
udp-queries 2450270 Number of UDP queries received
udp4-answers 2450270 Number of IPv4 answers sent out over UDP
udp4-queries 2450270 Number of IPv4UDP queries received
I'm hitting the server with 2.5 million synthetic queries which remain
constant. There are queries for CNAME, A, MX, NS, SOA, etc. which are
being sent in constant fashion to the PowerDNS server..
If I've studied the documentation correctly, it is good that qsize-q
is very low.
I don't understand why packetcache-miss / query-cache-miss are so
high. I'd have thought that the ttl of the query/negative-query would
answer the packet from the cache. Isn't that the case?
Sending the server a constant stream of identical queries (also
queries which result in NXDOMAIN or SERVFAIL) show expected results:
packetcache-hit 199997
packetcache-miss 6
packetcache-size 20
qsize-q 0
query-cache-hit 12
query-cache-miss 16
Can someone kindly help me with this, perhaps also pointing out
whether the cache parameters could be sensible?
BTW, Is there a method of configuring a packet cache size?
Thanks,
-JP
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